Furnaces for molten metal

ABSTRACT

A furnace for molten metal comprises a refractory bath to hold metal surrounding a heater which consists of a cup-shaped refractory vessel which stands in the bath and receives a highvelocity stream of hot gas directed into the mouth of the vessel from a fuel burner.

United States Patent King Jan. 18, 1972 [54] FURNACES FOR MOLTEN METALx1330 wogner "122/3283 I 2 o ner ...l2 3 1 inventor: David 2,642,1296/1953 1316666.... ..126/360 R [73] Assignee: Morganite Thermal DesingsLimited, Nor- 3,266,485 8/1966 Gino" 6 "126/360 R ton, Worcester,England 2,385,333 9/1945 Clapp et al ..266/33 2,603,476 7/1952 Whiston..266/33 [2 1 Flledr J y 22,1969 2,958,520 11/1960 Fritz ..266/33 1 APPL843582 FOREIGN PATENTS 0R APPLICATIONS 1 1 Foreign Application PriorityData 961,175 6/1964 Great Britain 266/33 July 25, 1968 Great Britain..35500/68 p i Examine,. Gel-a|d Dost Attorney-Larson, Taylor & Hinds[52] US. Cl ..266/33 R, 75/65 R, 126/360 R, 164/316, 266/34 R 5111111.61 ..C2lc 7/00 [57] ABSTRACT [58] Field 01' Search ..266/33, 34,39; 164/316; A furnam f molten metal comprises a refractory bath to75/65 R; 126/360 R1368 hold metal surrounding a heater which consists ofa cupshaped refractory vessel which stands in the bath and receivesReferences Cited a highwelocity stream of hot gas directed into themouth of UNITED STATES PATENTS the vessel from a fuel burner.

1,751,533 3/1930 Taylor... 126/360 R 4 Claims, 3 Drawing Figures2,299,122 10/1942 Battin ..126/360 R PATENIED JAN I 8 1912 SHEET 2 [IF 2FURNACES FOR MOLTEN METAL DESCRIPTION This invention relates to furnacesand provides a furnace suitable for melting metal and holding moltenmetal ready for use, such as in diecasting.

It is known to provide such a furnace consisting of a thermallyinsulated bath, to hold the molten metal, into which extends animmersion heater which may be an electrical heater or a conduit forflame from a fuel such as gas and air.

According to the present invention, a furnace comprisesa refractorybath, to hold molten metal up to a given level, a heat-conductiverefractory vessel supported in the bath in an upright position andspaced inwardly from the wall of the bath, so that molten metal cansurround the vessel in the bath, said vessel having an upwardly directedmouth above the given metal level, and a fuel burner for producing ahighvelocity stream of hot gas directed downwardly into the mouth of thevessel, the inner surface of the vessel forming a reversing baffle, fordownward impingement and reverse flow upward of the stream of hot gas,and the vessel having an outlet for hot gas above the given metal level.

It is an important feature of the invention that a stream of hot gas, asdistinct from flame, is used to heat the refractory vessel. The hottestpart of a flame from a simple burner is at some point within theboundaries of the flame which therefore has a diminishing temperaturegradient towards the outside. It is however possible to produce from asuitable burner, a highvelocity stream of hot gas more uniform intemperature than a flame and which can therefore, more efiiciently thana flame, uniformly heat to a high temperature a body having a surfaceswept by the hot gas stream and particularly a vessel of which theinside surface forms a reversing baffle for the hot gas stream.

A gas-air burner suitable for producing a high velocity stream of hotgas is described in United Kingdom Pat. Specification No. 1,100,156 andsuch a burner is preferred for use with the present invention.

An open-mouthed refractory vessel suitable for use with the inventionmay be similar to, or actually consist of, a cupshaped crucible such asis well known for holding molten metal in foundry work and which is madeof a refractory material of high thermal conductivity, such asclay-graphite.

The invention is illustrated, by way of example, on the accompanyingdrawings, in which:

FIG. 1 is a longitudinal section through a furnace,

FIG. 2 is a cross section on the line IIII of FIG. 1, and

FIG. 3 is a cross section similar to FIG. 2 but showing a modification.

The furnace illustrated by FIGS. 1 and 2 comprises a bath consisting ofa casing l, which may be of metal or brickwork, having an intermediatelining 2, of a refractory, thermally insulating material such asdiatomaceous brick, and an inner lining 3, of a refractory materialresistant to molten metal such as a cast refractory.

As shown by FIG. 1, the bath has a sloping end forming an inlet 4through which are fed billets 5 of metal to be melted, a flap 6 beingprovided to close the inlet.

The top of the bath is closed, except for a ladling opening 7 and a flue8, by a cover 9 having intermediate and inner linings l0 and 11 ofmaterials similar to those of the linings 2 and 3. An inverted weir l2depends into the bath from the cover lining 11 down to below a normalmolten metal level X--X so as to close off the ladling opening 7 fromthe space above the metal level from which hot gases can exhaust throughthe flue 8. A part 9A of the cover is hinged to form an inspecfion door.

Above the center of the bath, the inner lining ll of the cover embodiesa downwardly directed nozzle 13 for a highvelocity stream of hot gas,from a high-pressure gas-air burner 14 mounted in the cover 9, to entera clay-graphite, cupshaped refractory vessel 15 mounted on a plinth l6on the bottom of the bath.

The vessel 15 is of such size that. it has a surrounding clearance fromthe wall of the bath, to provide space for molten metal, and the mouthof the vessel 15 opens above the metal level and with an annularclearance around the nozzle 13.

The burner 14 is fed, through pipes 17, with air and gas under pressureso as to produce a high-velocity stream of very hot gas which impingescentrally at the base of the inner surface of the vessel 15 and isreversed, by the baffle effect of such surface, to sweep upwardly overthe surface and exhaust around the nozzle 13, over the surface of themetal in the bath and out through the flue 8.

The clay-graphite vessel 15, having a high thermal conductivity, becomesheated by the hot gas and transmits heat to the surrounding metal in thebath, the transfer of heat taking place very efficiently throughconduction and convection from the center outwards.

FIG. 3 shows a modified construction in which the rim of the vessel 15enters a groove 18 around the nozzle 13, which closes the mouth of thevessel 15, and a ring of outlet ports 19 for the hot gas is providedthrough the rim of the vessel 15. This arrangement enables the maximumrate of exhaust of hot gas from the vessel 15, and thus the heattransfer time, to be selected to conform to a designed optimum.

I claim:

1. A furnace comprising a refractory bath, to hold molten metal up to agiven level, a heat-conductive cup-shaped refractory vessel supported inthe bath in an upright position and spaced inwardly from the wall of thebath, so that molten metal can surround the vessel in the bath, saidvessel having an upwardly directed mouth above the given metal level andclosed by a downwardly directed nozzle for passing a highvelocity streamof hot gas from a fuel burner downwardly into the mouth of the vessel,the position surface of the vessel forming a reversing battle fordownward impingement and reverse flow upward of the stream of llrot gas,and the vessel having an outlet for hot gas above the given metal levelconstituted by ports through the rim of the vessel.

2. A furnace according to claim 1, in which the furnace has a cover, theburner is mounted in the cover and the cover has a refractory lining,part of which forms the downwardly directed nozzle for the stream of hotgas, leading from the burner into the vessel.

3. A furnace according to claim 2, in which the cover is provided with aladling opening and an inverted weir depending into the bath between theladling opening and the vessel.

4. A furnace according to claim 1, including a narrow foot supportextending between the bottom of the bath and the base of the vessel andspaced inwardly from the wall of the bath, such that molten metal cansurround the vessel and the bath.

I l t i UNITED STATES PATENT OFFICE. CERTIFICATE OF CORRECTION DatedJanuary 18, 1972 Patent No. 3,635,457

Invent0r(s DAVID KING It is certified that error appears in theabove-identified pat and that said Letters Patent are hereby correctedas shown below:

Claim 1, at column 2, line 44, "nosition" should be -inner-.

Signed and sealed this 6th day of June 1972.

(SEAL) Attast:

EDWARD M.FLETCHER,JR. ROBERT GO'I'TSCHALK Attesting Officer Commissionerof Patents USCOMMDC 60376-P69 9 US GOVERNMENT PRINTING OFFICE: 19590365-334 FORM po-wso mo se)

1. A furnace comprising a refractory bath, to hold molten metal up to agiven level, a heat-conductive cup-shaped refractory vessel supported inthe bath in an upright position and spaced inwardly from the wall of thebath, so that molten metal can surround the vessel in the bath, saidvessel having an upwardly directed mouth above the given metal level andclosed by a downwardly directed nozzle for passing a high-velocitystream of hot gas from a fuel burner downwardly into the mouth of thevessel, the position surface of the vessel forming a reversing bafflefor downward impingement and reverse flow upward of the stream of hotgas, and the vessel having an outlet for hot gas above the given metallevel constituted by ports through the rim of the vessel.
 2. A furnaceaccording to claim 1, in which the furnace has a cover, the burner ismounted in the cover and the cover has a refractory lining, part ofwhich forms the downwardly directed nozzle for the stream of hot gas,leading from the burner into the vessel.
 3. A furnace according to claim2, in which the cover is provided with a ladling opening and an invertedweir depending into the bath between the ladling opening and the vessel.4. A furnace according to claim 1, including a narrow foot supportextending between the bottom of the bath and the base of the vessel andspaced inwardly from the wall of the bath, such that molten metal cansurround the vessel and the bath.